Sensitive detection of photoexcited carriers by resonant tunneling through a single quantum dot

We show that the resonant tunnel current through a single energy level of an individual quantum dot within an ensemble of dots is strongly sensitive to photoexcited holes that become bound in the close vicinity of the dot. The presence of these holes lowers the electrostatic energy of the quantum dot state and switches the current carrying channel from fully open to fully closed with a high on/off ratio (> 50). The device can be reset by means of a bias voltage pulse. These properties are of interest for charge sensitive photon counting devices.Comment: 5 pages, 4 figure

Low-energy Dipole Excitations in Nuclei at the N=50,82 and Z=50 Shell Closures as Signatures for a Neutron Skin

Low-energy dipole excitations have been investigated theoretically in N=50, several N=82 isotones and the Z=50 Sn isotopes. For this purpose a method incorporating both HFB and multi-phonon QPM theory is applied. A concentration of one-phonon dipole strength located below the neutron emission threshold has been calculated in these nuclei. The analysis of the corresponding neutron and proton dipole transition densities allows to assign a genuine pattern to the low-energy excitations and making them distinct from the conventional GDR modes. Analyzing also the QRPA wave functions of the states we can identify these excitations as Pygmy Dipole Resonance (PDR) modes, recently studied also in Sn and N=82 nuclei. The results for N=50 are exploratory for an experimental project designed for the bremsstrahlung facility at the ELBE accelerator.Comment: Nuclear Physics in Astrophysics III Conference, 26 - 31 March 2007, Forschungszentrum Dresden-Rossendorf, German

The quality of education as a primary concern of the sustainable development

The quality of higher education aimed at solving problems of the sustainable development in economy and society is considered in this article. The goal of the sustainable development is to ensure high quality level of life for the present day and future generations. Education plays a significant role in achievement of this goal. The task of education is to develop the comprehensive knowledge in all the elements of the sustainable development, such as: ecology, economy, social sphere, and the ways of their effective interaction. This article contains the results of the research in this area obtained by the scientists of the Management Department of the Ogarev Mordovia State University while preparing for the international conference “Lifelong Education for the Sustainable Development”. The surveys conducted among schoolchildren, students, teachers, employers and the representatives of the state authorities in several regions of the Russian Federation (the Republic of Mordovia, the Novosibirsk, Tambov, Penza, Moscow regions) allowed studying the public opinion on the quality of higher education in Russia and its compliance with the modern and future needs of the economy and society, on the necessity of permanent education, defining the ways of the further development and improvement of higher education in Russia for the benefit of the sustainable development. The study is funded by the Ogarev Mordovia State University.peer-reviewe

Thermal Bogoliubov transformation in nuclear structure theory

Thermal Bogoliubov transformation is an essential ingredient of the thermo field dynamics -- the real time formalism in quantum field and many-body theories at finite temperatures developed by H. Umezawa and coworkers. The approach to study properties of hot nuclei which is based on the extension of the well-known Quasiparticle-Phonon Model to finite temperatures employing the TFD formalism is presented. A distinctive feature of the QPM-TFD combination is a possibility to go beyond the standard approximations like the thermal Hartree-Fock or the thermal RPA ones.Comment: 8 pages, Proceedings of the International Bogolyubov Conference "Problems of Theoretical and Mathematical Physics", August 23 -- 27, 2009, Dubna, Russi

Probing the Nuclear Neutron Skin by Low-Energy Dipole Modes

Dipole excitations below the neutron threshold in neutron rich Sn isotopes are studied theoretically in the Quasiparticle-Phonon Model with HFB single particle input. Of special interest are the low-lying two-phonon 1- states and the Pygmy Dipole Resonance (PDR). The evolution of low-energy dipole excitations with neutron excess is investigated over the Sn isotopic chain including the experimentally unknown regions close to 132Sn. A dependence of the PDR strengths and centroid energies on the neutron skin thickness is found. Despite significant multi-phonon contributions to mean energies and transition strengths, the PDR states retain their one-phonon character. The fragmentation pattern is reduced with increasing neutron excess towards the N=82 shell closure which will be of advantage for future experimental work.Comment: 4 pages, 2 figure